In general, it is desirable to improve the quality of image display devices, such as a generic television set. From traditional cathode ray tube (CRT) display technology to current liquid crystal display (LCD) technology, image display quality has advanced significantly. However, the image, as a result of the transmitting and transferring process is typically different from the original image. Even given a same original image and transmitting process, image display devices with different configurations and display performances may show different output images. This phenomenon is referred to as “color shift,” and results from distortion that occurs during image signal transmission and image processing. In addition, individuals perceive differently when viewing an image of the same object. For example, Asians and Europeans, due to the iris color of a pupil, have different preferences with respect to warm and cold colors.
Accordingly, a generic image display device provides a color correction function to allow a user to adjust image display properties of the image display device to fit the user's preferences. Further, color adjustment of an image display device depends on the output properties of color temperatures. Color temperature is measured by a color temperature unit Kelvin. Various color temperatures define different colors along the spectrum. When the color temperature is set at lower value such as 2,000K to 3,000K, the output color is a warm color, a bright red. When the color temperature is set at a higher value, such as 8,000K to 10,000K, the output color is a cold color, a gentle blue. Traditionally, image display devices are preset according to customer requirements or set at standard color temperature 5,000K as a default color temperature before shipping from factories.
The output properties of an image display device can also be adjusted by related settings of the image display devices (such as color management or color compensation function used in the monitor display properties settings of a computer system) by a user. The parameters include brightness, contrast, sharpness, gamma value and color value. By adjusting these parameters, users can perform required adjustments on image signals output to an image display device to attain desired quality of image display.
By increasing and decreasing the level of, e.g., brightness, contrast, sharpness, and/or gamma value, the adjusted image is displayed in real-time on the screen with modified brightness, added or lowered contrast between colors, or gamma curve adjustment to allow the naked eye to perceive detailed layers of dark and bright colors of dark and bright images with settings at higher and lower gamma values.
The above adjustment to adjust the color uses red/green/blue values or gamma tables. In addition, users can adjust the gain/offset of the red/green/blue signals individually to generate desirable image display output.
Nonetheless, it is challenging to attain a desirable image display quality by only adjusting white color. In the above method, adjusting a parameter or performing an adjustment on one of the RGB colors results in changes to the adjustment of a parameter or adjustment of one of the RGB true colors made in a previous step. That is, one adjustment step on one parameter or one true color impacts other parameters and true colors. Thus, improved color adjustment methodologies are desirable.